RFR: 8265604: Support unlinked classes in dynamic CDS archive

[Calvin Cheung]

This change adds the capability of storing unlinked class in dynamic CDS archive.
Before this change, unlinked classes loaded by custom class loaders won't be store in dynamic CDS archive.
Unlinked old classes with version < JAVA_6_VERSION will also be supported by this change. Similar to the support for old classes in static CDS archive in [JDK-8261090](https://bugs.openjdk.java.net/browse/JDK-8261090).

Testing:

- [x] tiers1,2,3,4

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Commit messages:
 - 8265604: Support unlinked classes in dynamic CDS archive

Changes: https://git.openjdk.java.net/jdk/pull/4803/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4803&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265604
  Stats: 153 lines in 18 files changed: 73 ins; 35 del; 45 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4803.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4803/head:pull/4803

PR: https://git.openjdk.java.net/jdk/pull/4803